Field of the Invention
The present invention pertains to fittings for attaching line sets to indoor and outdoor HVAC units and joining refrigeration components. More specifically, the present invention pertains to crimp fittings that can be used to attach two conventional tube ends to each other. The crimp fittings are specifically adapted and configured to sealably connect tubes that are under significant pressure (such as tubes in HVAC and other high pressure refrigerant systems).
General Background
It is common practice to utilize copper, aluminum, or other appreciably malleable tube in refrigeration systems. While conventional soldering techniques can be used to join some of such tubes (copper tubes in particular), soldering or brazing can have disadvantages. For example, soldering/brazing typically involves the use of a torch, which creates an inherent fire risk. This can be problematic or prohibited in situations where high pressure tubes need to be joined in buildings while such buildings are open to the public. Additionally, soldering/brazing aluminum, while possible, is difficult and is generally considered not practical for joining refrigeration and HVAC lines. Moreover, heat from the brazing/soldering operation often causes oxidation on the inside surfaces of such tubes, unless the installer takes additional steps to avoid such oxidation (for example, by flowing a purging gas such as nitrogen through the tube while applying heat).
The use of crimp fittings to join tube ends is a known alternative to soldering/brazing in low pressure applications. While many crimping techniques have been used to join various types of tubes in various circumstances, the relatively high pressures associated with refrigeration and HVAC lines make it difficult to achieve leakless connections. Moreover, in many high pressure connections, such crimp fittings must carry axial tension loads induced by the pressure. Such axial loads and internal pressures can cause the tube ends to deform and separate from the crimp fitting. Such separation is particularly difficult to prevent when the tubes are appreciably malleable.